It is, generally, well known that most light rail passenger transit vehicles, such as trolleys, subway cars and the like, are capable of being independently operated as a single passenger transit vehicle and are often operated as a single vehicle, particularly, during times when passenger travel is at a low volume. It is also, generally, well known that there are times when such transit vehicles are operated as a unit of two, three, or even more such transit vehicles joined together, particularly, during times of high volume passenger travel, such as the morning and evening "rush hours". Accordingly, in order to permit the operation of such multiple car units, such transit vehicles must be provided with a coupling means at their forward and rearward ends for selectively joining and un-joining the transit vehicles together as the needs change.
Most railway passenger transit vehicles of the prior art have utilized simple "hook-type" couplers for joining the adjacent ends of one such vehicle to another, which are pneumatically, electrically or hydraulically operated to uncouple the coupler incident to the disjoining of such joined adjacent ends of railway transit vehicles. That is to say, the coupler hooks are normally spring biased to a coupling position so that when the coupler on one transit vehicle is brought into contact with another, the coupler hooks will automatically engage each other to effect a coupling. The pneumatic, electric or hydraulic control incorporates responsive hardware that merely re-positions the engaged hooks so that the two transit vehicles are not coupled together thereby permitting either one of the transit vehicles to be driven away from the other.
Hook type transit couplers utilize a pivotal hook disposed within a gathering core recessed within a coupler head and includes a biasing spring to bias the pivotal hook to closed or latch position. Therefore, when a pair of such coupler heads, one each attached to an end of a transit vehicle, are brought into contact, the gathering cores are aligned so that the hook in each gathering core will engage the hook in the other gathering core to physically lock the two coupler heads together. Each gathering core includes an externally operated, rotatable unlatching cam adapted to pivot each hook away from the other hook to an unlatch position for purposes of uncoupling a pair of joined transit vehicles. Because the rotatable uncoupling cam is triangular in form, a considerable degree of friction results between the working edge of the rotatable uncoupling cam and the hook member side surface against which the cam is acting. Because the action is entirely a sliding action, a considerable degree of wear results not only to the active camming surface of the uncoupling cam but also to the side surface of the hook member. To minimize such wear and to assure that the cam is freely rotatable, it is common practice to pack sufficient lubricant; i.e., grease, into the gathering core and particularly around the uncoupling cam to lubricate the frictional contacting interface surfaces.
Since the outward end of any uncoupled transit vehicle will naturally have an unused coupler, the gathering core in such an unused coupler will be exposed to the elements including dust, dirt and debris which will be attracted to and contained within the grease packing within the gathering core. Such contaminated grease will, of course, adversely affect the operation of the coupler and particularly the rotatable cam, often contributing to wear which the grease is intended to minimize, and even preventing proper operation of the uncoupling cam. Therefore, proper preventative maintenance requires that the gathering cores be periodically wiped and cleaned of old contaminated grease and replaced with fresh clean grease.